1. Field of the Invention
The present invention relates to a glass capillary array for fluorescence analysis and a manufacturing method thereof.
2. Prior Art
Fluorometric gel electrophoresis is widely used as a DNA fluorescence analysis method for gene analysis and the like. Electrophoresis has the advantages that, since real time detection is carried out using laser-excited fluorescence, both the sensitivity and the throughput are high. Various fluorescent substances suitable for use in electrophoresis have been developed (see, for example, xe2x80x9cBunsekixe2x80x9d (xe2x80x9cAnalysisxe2x80x9d), January 1999 edition, pages 25-33). DNA fluorescence analysis using electrophoresis is carried out by separating fluorescently labeled DNA fragments according to molecular weight using gel electrophoresis, irradiating the DNA fragments with a laser beam and detecting the fluorescence thus emitted by the fluorescent labels, and analyzing a succession of detection signals obtained.
In a conventional analyzer that uses electrophoresis, an array of glass capillaries each having a circular cross section passes through an optical cell filled with a buffer solution, and DNA fragments that migrate through the glass capillary array are analyzed using a laser beam. To minimize background light due to scattering, the glass capillaries are arranged in a single row along the direction of the horizontally irradiated laser beam.
However, with such an analyzer, because the glass capillaries have a circular cross section, the laser beam is scattered at the surface of the first glass capillary, and hence cannot be irradiated uniformly onto the following glass capillaries.
To combat this problem, either the glass capillaries are given a square cross section so that the angle of incidence of the laser beam on each of the glass capillaries is always zero and hence the influence of refraction of the laser beam is eliminated, or else the portion of the glass capillary array irradiated by the laser beam is removed so as to form buffer solution sheath flows. A device disclosed in Japanese Laid-open Patent Publication (Kokai) No. 9-152418 provides an example of the former, and a device disclosed in Anal. Chem., 1994, Vol. 66, pages 1021-1026 provides an example of the latter.
However, in the case of the device disclosed in Japanese Laid-open Patent Publication (Kokai) No. 9-152418, there are spaces between the glass capillaries, and hence the laser beam used in the measurement is scattered at the surface of each glass capillary, resulting in the intensity of the laser beam progressively decreasing as the laser beam passes through each glass capillary, and hence in there being a limit on the number of glass capillaries on which measurement can be carried out simultaneously.
Moreover, in the case of the device disclosed in Anal. Chem., 1994, Vol. 66, pages 1021-1026, a special buffer solution is required, and the structure of the analyzer is complicated.
It is an object of the present invention to provide a glass capillary array for fluorescence analysis which is capable of preventing reduction of the transmittance of a laser beam through the glass capillaries during electrophoretic DNA fluorescence analysis, and a method of manufacturing the glass capillary array.
To attain the above object, the present invention provides a glass capillary array for fluorescence analysis, comprising a plurality of glass capillaries each having a rectangular cross section and having an internal hole formed therein, the plurality of glass capillaries being arranged in a row along a direction of irradiation of a laser beam for fluorescence analysis, wherein the glass capillary array has a fluorescence analysis section comprising a portion of each of the glass capillaries positioned in a region including an optical axis of the laser beam and a vicinity thereof, and the glass capillaries are joined together substantially into a single body using a transparent material in at least the fluorescence analysis section.
With the above arrangement, reduction of the transmittance of the laser beam through the glass capillaries during electrophoretic DNA fluorescence analysis can be prevented.
Preferably, the difference between the refractive index of the transparent material and the refractive index of the mother glass of the glass capillaries is not more than 0.3. As a result, reduction of the transmittance of the laser beam through the glass capillaries can be prevented reliably.
More preferably, the above refractive index difference is not more than 0.3, and the number of glass capillaries joined together is in a range of 10 to 30. As a result, reduction of the transmittance of the laser beam through the glass capillaries can be prevented more reliably.
Alternatively, the above refractive index difference is not more than 0.2, and the number of glass capillaries joined together is in a range of 10 to 100. As a result, reduction of the transmittance of the laser beam through the glass capillaries can be prevented more reliably.
Preferably, the glass capillaries are joined together using a resin adhesive. As a result, the glass capillaries can be joined together easily.
Alternatively, the glass capillaries are joined together using glass frit. As a result, the glass capillaries can be joined together easily.
Alternatively, the glass capillaries are joined together by welding using a laser beam. As a result, the glass capillaries can be joined together reliably, and the difference between the refractive index of the transparent material and the refractive index of the glass capillaries can be made substantially zero.
To attain the above object, the present invention further provides a method of manufacturing a glass capillary array for fluorescence analysis, comprising the steps of arranging a plurality of glass capillaries, each having a rectangular cross section and having an internal hole formed therein, in a row along a direction of irradiation of a laser beam for fluorescence analysis, to form a glass capillary array having a fluorescence analysis section comprising a portion of each of the glass capillaries positioned in a region including an optical axis of the laser beam and a vicinity thereof, and joining the glass capillaries together substantially into a single body using a transparent material in at least the fluorescence analysis section.
With the above arrangement, reduction of the transmittance of the laser beam through the glass capillaries during electrophoretic DNA fluorescence analysis can be prevented.
Preferably, the glass capillaries are joined together using a resin adhesive. As a result, the glass capillaries can be joined together easily.
Alternatively, the glass capillaries are joined together using glass frit. As a result, the glass capillaries can be joined together easily.
Alternatively, the glass capillaries are joined together by welding using a laser beam. As a result, the glass capillaries can be joined together reliably, and the difference between the refractive index of the transparent material and the refractive index of the glass capillaries can be made substantially zero.
The above and other objects, features and advantages of the invention will become more apparent from the following detailed description taken in conjunction with the accompanying drawings.